By: David A Fein, MD
“Cut out the carbs and you can eat all you want and still lose weight”
It was a concept that made the Atkins Diet famous. Of course, Atkins couldn’t change the laws of thermodynamics. If you eat more calories than you burn, you gain weight. Instead, what Atkins had found was that a high carb diet was likely to make you even more hungry and when you cut out the carbs you just simply ate less. Something about a high carb diet causes you to crave more carbs.
We have noticed over the years that some people seem like they are “carboholics”. They can eat large amounts of meat and low carb vegetables but still not feel like their appetite is satisfied until they have something like bread, dessert, a cookie or some other food that will quickly raise their blood sugar level. These people also tend to have evidence of Insulin Resistance.
Combine a high carb diet with a genetic predisposition and lack of exercise and you will very likely start to develop Insulin Resistance. Insulin is the hormone that tells certain cells to start taking sugar out of the bloodstream and bring it into the cell to be used for energy production or converted in storage as glycogen or fat. In people who are insulin resistant, those cells don’t respond in the usual way to insulin which can lead to higher than normal blood sugar levels. In order to try to keep blood sugar in the normal range, the body produces even more insulin until the insulin levels become high enough to overcome the resistance. So, people with insulin resistance usually have higher than normal insulin levels. Could it be that those of us who are “carboholics” are actually addicted to keeping our insulin levels high?
Interesting new research out of the Technical University of Munich may have found evidence to support this concept.
The metabolism of the brain is unique. Other organs can use fat as an energy source when sugar levels decline. Your brain relies entirely on glucose for its metabolism. Your brain also has the advantage of controlling hunger sensations so it is in a good position to control your desire for sugar to support your glucose levels.
The researchers found that the movement of glucose into the brain was not the passive process that it had previously been thought to be. Instead, it is controlled by specialized support cells in the brain called Astrocytes. The activity of the Astrocytes in bringing glucose into the brain was tied to insulin. If the receptors on the Astrocytes were missing or less active, the result was less activity in neurons in the brain including those that regulate appetite.
Other researchers have recently shown that Astrocytes also react to leptin, a hormone that plays a very important role in regulating hunger.
More research is needed. But it may turn out that insulin resistance has effects directly in the brain that lead to the brain needing higher levels of insulin in order to meet its glucose requirements. If so, this could explain why insulin resistance can make it so hard to change your eating habits and lose weight.